The present invention relates to a circuit breaker such as an auto-breaker, and more particularly to a trip indicating means thereof.
A circuit breaker has an over current tripping device for protecting a circuit and a device from an over current through tripping a switching mechanism to open a contact when an over current caused by overloading or short circuit in a main circuit is detected. The over-current tripping device has a time delay tripping device (bimetal type) that trips the switching mechanism with a delay corresponding to a magnitude of an overload current, and an instantaneous tripping device (electromagnetic type) that trips the switching mechanism instantaneously in response to a large current such as a short circuit current.
As an option, an alarm switch may be attached to the circuit breaker for indicating that the switching mechanism trips instantaneously when the short circuit current flows. When the circuit breaker trips in response to the short circuit current, the alarm switch attached to the circuit breaker sends a signal to the outside indicating the tripping.
With reference to FIGS. 6(a), 6(b), 7 and 8, a construction, and operation of the circuit breaker and the alarm switch attached to a main body of the circuit breaker will be explained. In FIGS. 6(a) and 6(b), a reference numeral 1 denotes a circuit breaker; a reference numeral 2 denotes a housing of the main body of the circuit breaker 1; a reference numeral 3 denotes a manual operating handle attached to a housing cover of the housing 2; a reference numeral 4 denotes an alarm switch attached to a side of the circuit breaker 1; and a reference numeral 5 denotes a trip indicating rod incorporated in the alarm switch 4. The trip indicating rod 5 is normally disposed inside a housing of the alarm switch 4. When the circuit breaker 1 trips instantaneously in response to the short circuit current, the trip indicating rod 5 is protruded from an upper side of the housing of the alarm switch 4 to indicate that the circuit breaker 1 instantaneously trips.
FIG. 7 is an assembly showing structures of a switching mechanism and an over-current tripping device incorporated in the circuit breaker 1. In FIG. 7, a reference numeral 6 denotes a switching mechanism for contacts: a reference numeral 6a denotes a swing type latch receiver incorporated in the switching mechanism 6; a reference numeral 6b denotes a transmission gear connected to the operating handle 3; a reference numeral 7 denotes a bimetal type time delay tripping device; a reference numeral 8 denotes an electromagnetic instantaneous tripping device; a reference numeral 8a denotes an electromagnetic coil; a reference numeral 8b denotes a plunger; a reference numeral 8c denotes a trip actuator attached to the plunger 8b; and a reference numeral 9 denotes a trip member for connecting the trip actuator 8c of the instantaneous tripping device 8 to the latch receiver 6a of the switching mechanism 6. The trip member 9 slides up and down to drive the latch receiver 6a to a release position in response to the operation of the instantaneous tripping device 8. The bimetal type time delay tripping device 7 is constructed such that an operating end of a bimetal thereof is connected to the latch receiver 6a via a temperature compensating bimetal, which is also used as an actuator lever, without going through the trip member 9.
FIG. 8 is a view showing a structure of the trip member 9 and a connection structure between the trip member 9 and the alarm switch 4. The trip member 9 formed of a resin plate is guided and supported to slide up and down in the breaker housing 2, and is urged upward by a return spring 10 inserted between the trip member 9 and a bottom of the breaker housing 2. The trip actuator 8c of the instantaneous tripping device 8 faces a shoulder part of the trip member 9. An end of the latch receiver 6a is inserted into a window hole with a cam surface formed on a surface of the trip member 9. The alarm switch 4 is comprised of the trip indicating rod 5 and an actuator lever 4a connected to an alarm contact point (not shown). An end of the actuator lever 4a is protruded into the housing 2 of the circuit breaker 1 and inserted into a concaved groove formed in a side of the trip member 9.
With the above arrangement, when a large current such as the short circuit current flows through a main circuit of the circuit breaker 1, the instantaneous tripping device 8 in FIG. 7 is operated to cause the trip actuator 8c thereof to push down the trip member 9 against the force of the return spring 10. Then, the latch receiver 6a tilts leftward to unlock a latch of the switching mechanism 6 (refer to FIG. 7) to cause the circuit breaker 1 to trip instantaneously. When the trip member 9 moves downward during the tripping, the actuator lever 4a of the alarm switch 4 turns counterclockwise. In response to the movement of the actuator lever 4a, the alarm contact point is turned on to transmit a trip signal to the outside, and the trip indicating rod 5 is pressed by a spring (not shown) to protrude from the housing 2 to indicate that the circuit breaker 1 instantaneously trips. The structure and operation of the switching mechanism 6 have been disclosed in detail in Japanese Patent Publication (KOKAI) No. 2001-23499 filed by the applicant of the present invention.
Further, the operating handle 3 of the circuit breaker 1 shown in FIGS. 6(a) and 6(b) is turned to a TRIP position located between an ON position and an OFF position in response to the tripping of the circuit breaker 1. Thus, it is possible to visually confirm that the circuit breaker 1 is tripped according to the position of the operating handle 3. In this case, it is difficult to determine whether the circuit breaker is tripped due to the overload current or the short circuit current.
As described above, the main body of the conventional circuit breaker can not indicate that the circuit breaker trips instantaneously. It is therefore necessary to provide the alarm switch in the main body of the circuit breaker as an attachment (option) so as to indicate whether the circuit breaker trips instantaneously. Therefore, even if a user does not need a function of transmitting an electric signal indicating that the circuit breaker trips instantaneously, and just needs to visually confirm that the circuit breaker trips instantaneously, the user has to obtain a space for installing the alarm switch.
It is therefore an object of the present invention to provide a circuit breaker that makes it possible to visually confirm that, the circuit breaker instantaneously trips due to a short circuit current only by adding a simple part to a tripping mechanism of the circuit breaker, thereby improving safety by holding the tripping mechanism at a trip position until the breaker is reset.
Further objects and advantages of the invention will be apparent from the following description of the invention.
To attain the above object, according to the present invention, a circuit breaker includes a switching mechanism for switching contacts, a manual operating handle connected to the switching mechanism, and an instantaneous tripping device for detecting a short circuit current and opening the contacts of a main circuit. In the circuit breaker, the instantaneous tripping device and a latch receiver of the switching mechanism are connected with each other via a trip member capable of sliding up and down. The trip member slides in response to a movement of the instantaneous tripping device, and drives the latch receiver to a release position to trip the switching mechanism. Further, the circuit breaker includes a trip indicating member attached to the trip member, and a trip indicating window formed in a breaker housing and facing the trip indicating member. The trip indicating member moves to an indicating position to visually indicate a tripping state of the circuit breaker through the trip indicating window when the circuit breaker instantaneously trips.
The trip indicating member is formed of a strip or band piece having one end connected to the trip member and a leading end provided with an engagement protrusion for identifying the tripping state. The leading end of the strip piece is situated at a backside of the trip indicating window formed in the breaker housing. When the circuit breaker trips instantaneously, the engagement protrusion is inserted into the trip indicating window to indicate that the circuit breaker instantaneously trips.
In addition to the configuration described above, the circuit breaker may be provided with a release lever connected to the manual operating handle provided on a cover of the breaker housing for releasing the engagement protrusion of the trip indicating member from the trip indicating window through a reset operation by the manual operating handle.
An engagement protrusion as the trip indicating member for indicating the tripping state may be provided at a side edge of the trip member. The trip indicating window corresponding to the engagement protrusion is formed in a side wall of the breaker housing.
With the above arrangement, the engagement protrusion provided at the leading end of the trip indicating member for identifying the tripping state normally stays at a position away from the trip indicating window formed in the housing. When the circuit breaker trips instantaneously in response to a flow of the short circuit current, the trip member slides to a trip position in response to an operation of the instantaneous tripping device. Along with the sliding movement of the trip member, the engagement projection of the trip indicating member moves from the retracted position to the indicating position, so that the engagement projection is inserted into the trip indicating window and locked within a frame thereof at the same time. In this state, whether the circuit breaker trips instantaneously can be visually confirmed through the trip indicating window from the outside. As the trip member is locked at the trip position, the circuit breaker can not be turned on again.
After confirming that a circuit or equipment connected to the circuit breaker is recovered, the engagement protrusion of the trip indicating member is released from the trip indicating window to return the trip member to the original position, and the operating handle is turned to a reset position to allow the circuit breaker to turn on again. In this case, in order to release the engagement protrusion of the trip indicating member from the trip indicating window, the engagement protrusion is pushed from the trip indicating window by such a tool as a driver, or the release lever provided in the operating handle is turned to the reset position for releasing the engagement protrusion of the trip indicating member from the trip indicating window.